In various measurement and regulating tasks, it is necessary to measure the pressure of a gas, either as an absolute value, or as a relative value with respect to a second pressure. Examples of such uses would be measuring the intake tube pressure of an internal combustion engine of a motor vehicles, measuring the filling level, or measuring blood pressure electrically in medical technology, among others. An induction difference pressure sensor is disclosed in Swiss Pat. No. 489,792, in which two coil devices, connected in a bridge circuit, interact in push-pull fashion with a diaphragm which is deflectable in accordance with a differential pressure. The inductance of the respective coils or coil devices varies as a function of the deflection of the diaphragm, causing a shift in the frequency of an oscillator, in which the coils are frequency-determining elements.
However, the known apparatus uses cup-shaped ferrite cores for the coils, which necessarily results in a bulky structure. Further, most prior art sensors make no particular provision for preventing the oscillator frequency from drifting due to temperature fluctuations.